Propellants containing copolymers of dienes and polymerizable ferrocene or carborane compounds

ABSTRACT

COPOLYMERS OF A DIENE SELECTED FROM THE BUTADIENE, ISOPRENE, AND CHLOROPRENE AND A POLYMERIABLE MONOMER SELECTED FROM FERROCENYLBUTADIENE, 2-FERROCENYLBUTADIENE, FERROCENE,1-FERROCENYLBUTADIENE, 2-FERROCENYLBUTADIENE, VINYLCARBORANE, ISOPROPENYLBUTADIENE AND CARBORANYLMETHYL ACRYLATE ARE DISCLOSED ALONG WITH PREPARATIVE PROCEDURES THEREOF. COPOLYMERIZATIONS ARE CARRIED OUT IN SOLUTION (TOLUENE OR DIOXANE) WITH A SUITABLE POLYMERIZATION INITIATOR SELECTED FROM AN AZO COMPOUND TO INTRODUCE EITHER CARBOXYL OR HYDROXYL FUNCTIONALITY INTO THE COPOLYMERS.

United States Patent Oflice 3,813,304 PROPELLANTS CONTAINING COPOLYMERS F DIENES AND POLYMERIZABLE FERROCENE 0R CARBORANE COMPOUNDS Samuel F. Reed, In, Holland, Pa., assignor to the United States of America as represented by the Secretary of the Army No Drawing. Original application June 18, 1971, Ser. No. 155,669. Divided and this application Oct. 25, 1972, Ser. No. 300,039

Int. Cl. (306d 5/06 US. Cl. 149-193 3 Claims ABSTRACT OF THE DISCLOSURE Copolymers of a diene selected from butadiene, isoprene, and chloroprene and a polymerizable monomer selected from ferrocenylmethyl methacrylate, isopropenylferrocene, l-ferrocenylbutadiene, Z-ferrocenylbutadiene, vinylcarborane, isopropenylcarborane and carboranylmethyl acrylate are disclosed along with preparative procedures therefor. Copolymerizations are carried out in solution (toluene or dioxane) with a suitable polymerization initiator selected from an azo compound to introduce either carboxyl or hydroxyl functionality into the copolymers.

CROSS-REFERENCE TO RELATED APPLICATION This is a division of application Ser. No. 155,669, filed June 18, 1971.

BACKGROUND OF THE INVENTION Considerable literature exists on the preparation of polydienes of the telechelic type prepared by both anionic and free radical initiators.

Well known in the propellant field is the fact that the burning rate of many solid propellants can be increased by the introduction of certain additives. Many ferrocene or carborane derivatives have been utilized as additives for this purpose, usually in the form of liquids in which state they also serve as plasticizing agent. In the liquid state the additives exhibit the inherent disadvantages characteristic of liquid additives such as loss by evaporation, migration, etc., and consequently, the propellant systems suffer, particularly on long term storage.

Thus, a need exists for a modified form of ferrocene or carborane additive which form is not subject to being lost by evaporation or migration from a stored propellant composition.

An object of this invention is to combine a selected ferrocene or carboraneadditive with the binder being utilized in the propellant system.

Another object is to combine the selected ferrocene or carborane additive and the binder material via a polymerization technique into a serviceable prepolymer suitable for propellant mixing and curing.

A specific object of this invention is to copolymerize a binder material and a catalyst material to provide a liquid copolymer which is capable of undergoing a cure reaction when used in a propellant composition to form a rubber-like binder material having a burning rate catalyst agent as an integral part thereof.

SUMMARY OF THE INVENTION Copolymers of dienes selected from butadiene, isoprene, and chloroprene and polymerizable monomers selected from ferrocenylmethyl methacrylate (FMMA), isopropenylferrocene (IPF), l-ferrocenylbutadiene (l-FB), 2- ferrocenylbutadiene (Z-FB), vinylcarborane (VC), isopropenylcarborane (IPC), and carboranylmethyl acrylate (CMA) are prepared through free radical copolymerize.- tion in an inert organic solvent (e.g. toluene or dioxane) using an azo compound initiator selected from azobis (2- methyl valeric acid) (AMCV), 4,4'-azobis (4-cyanopentanoic acid) (ACPA), and 4,4'-azobis (4-cyano-npentanol) (HMHV). The reaction periods may vary from about 72-96 hours while the reactor is maintained at a temperature from about 66-67 C. Comonomer weight ratios may be varied from about 1:1 to about 19:1 (diene to monomer weight ratio). Physical properties of flue c0- polymers may best be controlled by varying the initiator concentration. The copolymers are characterized by molecular weights in the range from about 1,500 to about 10,000, and end group (CO H or OH) from about 0.1 to about 5.0 weight percent. Boron contents of the copolymers may be varied from about 0-30 weight percent; iron contents of the copolymers may be varied from about 0-15 weight percent.

DESCRIPTION OF THE PREFERRED I EMBODIMENTS The copolymers of this invention are liquids which contain terminal groups (CO H or OH) and are capable of undergoing a cure reaction to a final rubber-like state. The usefulness of these copolymers is directed to their application as binders in high burning rate solid propellants.

The general descriptive technique of polymer preparation is set forth below for the diene, butadiene, and the monomer, carboranylmethyl acrylate (CMA). Following this descriptive technique will be Tables IVIII which illustrate the experimental data on preparation of other copolymers and physical property data for the particular copolymers set forth.

A general descriptive technique employed in the copolymerization of butadiene and CMA and used in all other copolymerizations is as follows: to a glass highpressure reactor (aerosol tube) are introduced 30 ml. of dioxane, 1.0 g. (3.34 mmoles) CMA and 3.28 g. (10.7 mmoles) azobis (Z-methyl valeric acid) (AMCV). The reactor is attached to a vacuum line and deaerated by three alternate freeze-thaw cycles. At this point 19.0 g. (252 mmoles) of butadiene are condensed into the reactor, and the reactor is removed from the vacuum line and placed in an oil bath at 6667 C. Heating is continued for a period of 72 hours. On cooling, the reactor is vented, the solvent removed by evaporation, and the copolymer reprecipitated by dissolving in ether followed by the addition of methanol. After decanting the solvents, the copolymer is stripped of excess solvents on a rotary evaporator, and finally dried at 70-75 C. under reduced pressure (1 mm.) for a period of 24 hours. The liquid copolymer is then characterized by its molecular weight, hydroxy-end group content and elemental analysis. These values are: molecular weight'3,500, carboxyl-end group content-2.56, boron-2.55 percent (calculated 2.37 percent).

The experimental data for examples of other copolymerizations are given in the following Tables (IVIII). Comonomer weight ratios are varied from approximately 1:1 to 19:1. Physical properties of the copolymers may best be controlled by varying the initiator concentration. It is reasonable to expect molecular weights in the range of 1,500-10,000 and end group (CO H or OH) from 0.1 to 5 .0. Boron contents of the copolymers may be varied from 0-30 weight percent; iron content from 0-15 weight percent.

TABLE I..E 31;;ERIMENTAL DATA ON PREPARATION OF TADIENE-CMA COPOLYMERS [Temp 65-72 hours] G./mmoles Weight Buteratio, Weight diene Bd/ (AM CV polymer Yield, N 0. (Bd) CMA CMA mmoles) (g.) percent TABLE II.PHYSICAL PROPERTY DATA ON BUTADIENE/ CMA COPOLYMERS COPOLYMERS OF ISOPRENE--FMMA TABLE VIIL-PHYSIOAL PROPERTY DATA ON BUTADI- I ENE/l-FB COPOLYMERS Percent Fe Molecular Weight wei ht percent; Calcu- Number n) COzH lated Found The effectiveness of copolymers of this invention as a binder-burning rate catalyst is illustrated by combining the copolymer with a plasticizer, a metal additive, and an inorganic oxidizer. A test propellant composition comprised of a selected copolymer having about a 1 weight percent iron (Fe) or a selected copolymer having about a 1 weight percent boron (B) will provide an increase of at least 20 percent in the burning rate as compared with a standard propellant composition having a diene binder which does not contain iron or boron. The test propellant composition described above contained about 10 weight percent copolymer, 10 weight percent plasticizer (isodecyl TABLE III.-EXPERIMENTAL DATA FOR PREPARATION OF ISOPRENE- FMMA COPOLYMERS Molar G. (moles) ratio,

isoprene Solvent Weight (g.) Percent Number Isoprene FMMA AMHV FM ml.) copolymer yield 19 (352) 1 (3. 5) 2 69 (10.7) 100.5 Dioxane 12.5 53.5 17 (315) 3 (10.5) 2.46 (9.8) 30.0 o 11.7 58.5 15 (277) 5 (17.5) 2. 23 (8.8) 15.8 o 15.0 75.0 10 (185) 10 (35) 1.65 (6.6) 5.3 o 17.6 88.0

TABLE IV.PHYSICAL PROPERTY DATA ON ISOPRENE/ FMMA COPOLYMERS Weight Percent Fe Molecular percent Number weight 0H Calculated Found COPOLYMERS OF BUTADIENE-ISOPRO-PENYL- FERR'OCENE (I'PF) pelargonate), 10 weight percent metal additive (aluminum powder) and up to about Weight percent inorganic oxidizer (ammonium perchlorate).

The copolymers of this invention may be used in varying amounts from about 5 to about 30 weight percent of the propellant composition. Since the weight percent of the metallic containing monomer can also be varied over a wide range in preparing the copolymer, propellant compositions having a wide range of burning rates can be pre- TABLE V.EXPERIMENTAL DATA FOR PREPARATION OF BUTADIENE- IPF COPOLYME RS [Temp. 65 C.Time 72 hours] G. (mmoles) Bute- Molar Weight dicne ratio, Solvent (g.) Percent No (Bd) IPF AMHV Bd/IPF (30 ml.) copolymcr yield 79. 64 Dioxane- 14. 4 72. 2 13. 0 65. 0 15. 4 75. 2 14. 4 72. 2

TABLE VI.PHYSICAL PROPERTY DATA ON BUTADIENE/IPF COPOLYMERS Molecular Weight Percent Fe weight percent (M8) OH Calculated Found COPOLYMERS OF BUTADIENE1-FERROCENY'L- BUTADIENE (1-FB) pared using the copolymers of this invention. Also, on the 5 basis of requirements, copolymers may be prepared which contain the iron catalyst component or the boron catalyst component. The burning rates of propellant compositions vary with an increase in the metal content of the catalystbinder copolymers contained in the propellant compositions. Catalysts compounds containing iron, boron, or combinations thereof have been proven to be efi'ective catalysts; however, the use of these metal compounds in a curable rubber-like polymer makes them even more attractive due to stability from migration, improvement to physi- TABLE VII-EXPERIMENTAL DATA FOR PREPARATION OF BUTADI- ENE-l-FB COPOLYME R G. (mmoles) olar ratio, Weigh Butadi- Bd/1 Solvent (g.) 00- Yield, No ene (Bd) 1-FB AMVC FB (30 ml.) polymer percent 1 (4.2) 2.996 (10. 7) 83.8 Dioxane..- 13.7 68.5 3 (12.6) 2. 744 (9.8) 10.5 50.2 5 (21) 2.24 (9) 7.5 37.5 10.0 (42) 1.904 (6.8) 5.2 26.0

cal properties etc. Other plasticizers, metal additives, or oxidizing salts may be used with the copolymers of this invention since these copolymers are compatible and curable with a wide variety of propellant ingredients.

I claim:

1. A propellant composition comprised of a plasticizer, a metal additive, an inorganic oxidizer, and selected copolymers as a binder-burning rate catalyst, said selected copolymers being selected from the copolymers prepared by the method of polymerizing a diene selected from butadiene, isoprene, and chloroprene and a polymerizable monomer selected from ferrocenylmethyl methacrylate, isopropylferrocene, and l-ferrocenylbutadiene to yield copolymers characterized by having an iron content up to about 15 weight percent and a polymerizable monomer selected from vinylcarborane and isopropenylcarborane to yield copolymers characterized by having a boron content up to about 30 weight percent, said method comprising reacting said polymerizable monomer and a suitable polymerization initiator in an inert organic solvent with said diene at a reaction temperature and for a reaction time period sufficient for said reaction to take place after which solvent removal is effected and said copolymers are dried at a suitable drying temperature while under reduced pressure; said initiator being selected from the azo initiators consisting of azobis(2-methyl valeric acid) and 4,4-azobis(4-cyanopentanoic acid) to yield copolymers characterized by having a weight percent of CO' H terminal groups from about 1.45 to about 4.33, and said initiator being 4, 4-azobis(4-cyano-n-pentanol) to yield copolymers characterized by having a weight percent of OH terminal groups from about 0.25 to about 3.03; said inert organic solvent being selected from dioxane and toluene; said reaction temperature being from about 66-67 C.; said reaction time being from about 72-96 hours; said drying is accomplished at a suitable temperature in the range of about 70 C. to about 75 C. and said reduced pressure is in the range of about 1 millimeter; said copolymers being further characterized by molecular weights in the range from about 1,500 to about 10,000.

2. The propellant composition of claim 1 wherein said copolymers are comprised of said diene and a polymerizable monomer selected from ferrocenylmethyl methacrylate, isopropenylferrocene, and 1-ferrocenylbutadiene, and wherein said copolymers are contained in said propellant composition in an amount from about 5 to about 30 weight percent, said plasticizer is isodecyl pelargonate in an amount of about 10 weight percent, said metal additive is aluminum powder in an amount of about 10 weight percent, and said inorganic oxidizer is ammonium perchlorate in an amount up to about weight percent.

3. The propellant composition of claim 1 wherein said copolymers are comprised of said diene and a polymerizable monomer selected from vinylcarborane and isopropenylcarborane and wherein said copolymers are contained in said propellant composition in an amount from about 5 to about 30 weight percent, said plasticizer is isodecyl pelargonate in an amount of about 10 weight percent, said metal additive is aluminum powder in an amount of about 10 weight percent, said metal additive is aluminum powder in an amount of about 10 weight percent, and said inorganic oxidizer is ammonium perchlorate in an amount up to about 70 weight percent.

References Cited UNITED STATES PATENTS 3,146,260 3/1964 Ager et a1 149 22 AX 3,183,216 5/1965 Cohen et al 149 22 UX 3,301,836 l/1967 Green et a1 14922 X 3,513,241 6/1970 Duling et al 26089.5 3,536,552 6/1971 Potts er al 149-20 X 3,593,350 3/1971 Dewey 149- 19 x FOREIGN PATENTS 601,243 7/1960 Canada 260-434 Cy OTHER REFERENCES Bamford et al.: Trans Faraday Soc., 56, 932- 942 (1960).

Horspool et al.: Can. J. Chem., 47, 3085-8 (1969).

Van Landuyt et al.: J. Polymer Science, Part A-l, 9, 523-529 (1971).

LELAND A. SEBASTIAN, Primary Examiner E. A. MILLER, Assistant Examiner US. Cl. X.R. l4944, 76 

